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c86b6ff551
mutex releases to not require flags for the cases when preemption is not allowed: The purpose of the MTX_NOSWITCH and SWI_NOSWITCH flags is to prevent switching to a higher priority thread on mutex releease and swi schedule, respectively when that switch is not safe. Now that the critical section API maintains a per-thread nesting count, the kernel can easily check whether or not it should switch without relying on flags from the programmer. This fixes a few bugs in that all current callers of swi_sched() used SWI_NOSWITCH, when in fact, only the ones called from fast interrupt handlers and the swi_sched of softclock needed this flag. Note that to ensure that swi_sched()'s in clock and fast interrupt handlers do not switch, these handlers have to be explicitly wrapped in critical_enter/exit pairs. Presently, just wrapping the handlers is sufficient, but in the future with the fully preemptive kernel, the interrupt must be EOI'd before critical_exit() is called. (critical_exit() can switch due to a deferred preemption in a fully preemptive kernel.) I've tested the changes to the interrupt code on i386 and alpha. I have not tested ia64, but the interrupt code is almost identical to the alpha code, so I expect it will work fine. PowerPC and ARM do not yet have interrupt code in the tree so they shouldn't be broken. Sparc64 is broken, but that's been ok'd by jake and tmm who will be fixing the interrupt code for sparc64 shortly. Reviewed by: peter Tested on: i386, alpha
224 lines
5.5 KiB
C
224 lines
5.5 KiB
C
/*-
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* Copyright (c) 2000 Doug Rabson
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* $FreeBSD$
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*/
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#include <sys/param.h>
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#include <sys/systm.h>
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#include <sys/bus.h>
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#include <sys/interrupt.h>
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#include <sys/kernel.h>
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#include <sys/lock.h>
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#include <sys/malloc.h>
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#include <sys/mutex.h>
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#include <sys/taskqueue.h>
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static MALLOC_DEFINE(M_TASKQUEUE, "taskqueue", "Task Queues");
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static STAILQ_HEAD(taskqueue_list, taskqueue) taskqueue_queues;
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static void *taskqueue_ih;
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static struct mtx taskqueue_queues_mutex;
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struct taskqueue {
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STAILQ_ENTRY(taskqueue) tq_link;
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STAILQ_HEAD(, task) tq_queue;
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const char *tq_name;
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taskqueue_enqueue_fn tq_enqueue;
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void *tq_context;
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int tq_draining;
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struct mtx tq_mutex;
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};
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static void init_taskqueue_list(void *data);
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static void
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init_taskqueue_list(void *data __unused)
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{
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mtx_init(&taskqueue_queues_mutex, "taskqueue list", MTX_DEF);
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STAILQ_INIT(&taskqueue_queues);
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}
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SYSINIT(taskqueue_list, SI_SUB_INTRINSIC, SI_ORDER_ANY, init_taskqueue_list,
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NULL);
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struct taskqueue *
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taskqueue_create(const char *name, int mflags,
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taskqueue_enqueue_fn enqueue, void *context)
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{
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struct taskqueue *queue;
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queue = malloc(sizeof(struct taskqueue), M_TASKQUEUE, mflags | M_ZERO);
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if (!queue)
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return 0;
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STAILQ_INIT(&queue->tq_queue);
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queue->tq_name = name;
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queue->tq_enqueue = enqueue;
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queue->tq_context = context;
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queue->tq_draining = 0;
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mtx_init(&queue->tq_mutex, "taskqueue", MTX_DEF);
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mtx_lock(&taskqueue_queues_mutex);
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STAILQ_INSERT_TAIL(&taskqueue_queues, queue, tq_link);
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mtx_unlock(&taskqueue_queues_mutex);
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return queue;
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}
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void
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taskqueue_free(struct taskqueue *queue)
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{
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mtx_lock(&queue->tq_mutex);
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queue->tq_draining = 1;
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mtx_unlock(&queue->tq_mutex);
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taskqueue_run(queue);
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mtx_lock(&taskqueue_queues_mutex);
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STAILQ_REMOVE(&taskqueue_queues, queue, taskqueue, tq_link);
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mtx_unlock(&taskqueue_queues_mutex);
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mtx_destroy(&queue->tq_mutex);
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free(queue, M_TASKQUEUE);
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}
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/*
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* Returns with the taskqueue locked.
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*/
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struct taskqueue *
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taskqueue_find(const char *name)
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{
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struct taskqueue *queue;
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mtx_lock(&taskqueue_queues_mutex);
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STAILQ_FOREACH(queue, &taskqueue_queues, tq_link) {
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mtx_lock(&queue->tq_mutex);
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if (!strcmp(queue->tq_name, name)) {
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mtx_unlock(&taskqueue_queues_mutex);
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return queue;
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}
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mtx_unlock(&queue->tq_mutex);
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}
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mtx_unlock(&taskqueue_queues_mutex);
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return 0;
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}
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int
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taskqueue_enqueue(struct taskqueue *queue, struct task *task)
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{
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struct task *ins;
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struct task *prev;
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mtx_lock(&queue->tq_mutex);
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/*
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* Don't allow new tasks on a queue which is being freed.
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*/
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if (queue->tq_draining) {
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mtx_unlock(&queue->tq_mutex);
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return EPIPE;
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}
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/*
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* Count multiple enqueues.
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*/
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if (task->ta_pending) {
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task->ta_pending++;
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mtx_unlock(&queue->tq_mutex);
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return 0;
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}
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/*
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* Optimise the case when all tasks have the same priority.
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*/
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prev = STAILQ_LAST(&queue->tq_queue, task, ta_link);
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if (!prev || prev->ta_priority >= task->ta_priority) {
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STAILQ_INSERT_TAIL(&queue->tq_queue, task, ta_link);
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} else {
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prev = 0;
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for (ins = STAILQ_FIRST(&queue->tq_queue); ins;
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prev = ins, ins = STAILQ_NEXT(ins, ta_link))
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if (ins->ta_priority < task->ta_priority)
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break;
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if (prev)
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STAILQ_INSERT_AFTER(&queue->tq_queue, prev, task, ta_link);
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else
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STAILQ_INSERT_HEAD(&queue->tq_queue, task, ta_link);
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}
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task->ta_pending = 1;
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if (queue->tq_enqueue)
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queue->tq_enqueue(queue->tq_context);
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mtx_unlock(&queue->tq_mutex);
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return 0;
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}
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void
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taskqueue_run(struct taskqueue *queue)
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{
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struct task *task;
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int pending;
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mtx_lock(&queue->tq_mutex);
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while (STAILQ_FIRST(&queue->tq_queue)) {
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/*
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* Carefully remove the first task from the queue and
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* zero its pending count.
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*/
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task = STAILQ_FIRST(&queue->tq_queue);
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STAILQ_REMOVE_HEAD(&queue->tq_queue, ta_link);
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pending = task->ta_pending;
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task->ta_pending = 0;
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mtx_unlock(&queue->tq_mutex);
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task->ta_func(task->ta_context, pending);
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mtx_lock(&queue->tq_mutex);
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}
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mtx_unlock(&queue->tq_mutex);
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}
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static void
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taskqueue_swi_enqueue(void *context)
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{
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swi_sched(taskqueue_ih, 0);
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}
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static void
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taskqueue_swi_run(void *dummy)
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{
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taskqueue_run(taskqueue_swi);
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}
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TASKQUEUE_DEFINE(swi, taskqueue_swi_enqueue, 0,
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swi_add(NULL, "task queue", taskqueue_swi_run, NULL, SWI_TQ, 0,
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&taskqueue_ih));
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